Flow dynamics around a rectangular bluff body under the impact of aspect ratios and Reynolds numbers

This work investigates the combined effect of Reynolds numbers (Re) and aspect ratios (AR = height/width) on flow features of a single vertically mounted rectangular cylinder using the lattice Boltzmann method. The Re and AR varied systematically from 75 to 200 and 0.5 to 4, respectively. Three distinct flow regimes: the steady flow, weak vortex shedding flow, and strong vortex shedding flow are identified based on the variations of AR and Re. It is found that aspect ratio as well as the viscosity variations noticeably influence the vortex dynamics and fluid forces. The average drag coefficient, the amplitudes of drag and lift coefficients as well as their rms values of drag and lift coefficients are found to be increasing with Re and AR. The Strouhal number decreased with increasing aspect ratios till AR = 3.5. At AR = 4, noticeable deviations resulting in sudden jumps in force parameters are observed, indicating a more complex interaction between the flow and the rectangle at high aspect ratios.